1. Field of the Invention
The present invention relates, in general, to a method of winding an armature coil on a cylindrical resin insulator of coreless motors and to a coreless motor produced through such a coil winding method and, more particularly, to an armature coil winding method, designed to allow a resulting coreless motor to effectively generate desired torque by an application of a low current so as to conserve electricity, and to simplify the production process of the motor so as to reduce the production cost of the motor, thus finally improving productivity and economical efficiency of the coreless motors, the present invention also relating to a coreless motor produced through such a coil winding method.
2. Description of the Prior Art
As well known to those skilled in the art, coreless motors are preferably used in portable communication instruments, such as pagers and cellular phones, so as to vibrate the instruments in the case of a calling of the instruments in a vibration mode.
Nowadays, many people use portable communication instruments, such as pagers and cellular phones, in accordance with a rapid development in the information intensive society. Conventional pagers and cellular phones (hereinbelow, referred to simply as xe2x80x9ccellular phonesxe2x80x9d) are typically designed to inform users of an incoming call through either a sound or vibration signal. In a crowded area, some users of such cellular phones preferably select or are forced to select a vibration mode in place of a sound mode since a sound signal may disturb those around the users. Coreless motors are set within cellular phones to accomplish such a vibration mode of the phones.
FIGS. 1 and 2 show conventional cup-type and bell-type armature coils of such coreless motors. Technology of such conventional armature coils of coreless motors may be preferably referred to some technical documents, for example, page 88 of xe2x80x9cManual of Control Motors, the Third Editionxe2x80x9d published by Sewoon Publishing Company of Korea on Feb. 5, 1995. As shown in FIG. 1, the conventional cup-type armature coil 1 has a cylindrical shape and consists of upper, middle and lower coil parts, with a shaft 2 axially passing through the center of the coil 1. At the upper and lower coil parts 3 and 4 of the armature coil 1, a coil is slantly wound at an angle of xcex8. However, at the middle coil part 5 of the armature coil 1, the coil is vertically wound at an angle of 90xc2x0.
Because of slantly wound coils of the upper and lower parts of the cup-type armature coil, the magnetic flux generated is not so effective that the torque is accordingly reduced. That is, when a current flows in the cup-type armature coil, the coil merely generates an ineffective magnetic flux, and so the torque is undesirably reduced by 1xe2x88x92sin xcex8. This is explained by the expression, F=Bil sin xcex8, wherein F is torque, B is a magnetic flux density, i is a current, l is a length of the conductive wire, and xcex8 is an angle between the current flowing in the conductive wire and an outside magnetic field.
That is, when the coils of the upper and lower coil parts 3 and 4 of the armature coil 1 are slantly wound at an angle of xcex8 (=60xc2x0), the torque is undesirably reduced by about 13.4% in comparison with the torque of the middle coil part 5 having a coil winding angle of 90xc2x0 since sin 60xc2x0 is less than sin 90xc2x0 (=1). In a brief description, the cup-type armature coil 1 of FIG. 1 merely generates low torque and always has low magnetic flux efficiency due to the slantly wound coils at the upper and lower coil parts 3 and 4.
As shown in FIG. 2, the conventional bell-type armature coil 1 is formed by diagonally winding a coil at an angle of xcex8, with a shaft 2 axially passing through the center of the coil 1. Due to such a diagonally wound coil, the bell-type armature coil merely generates an ineffective magnetic flux when a current flows in the coil, and so the torque is undesirably reduced by 1xe2x88x92sin xcex8. Therefore, the bell-type armature coil 1 does not generate full magnetic flux efficiency in the same manner as that described for the conventional cup-type armature coil of FIG. 1.
Therefore, the conventional armature coils of FIGS. 1 and 2, having low magnetic flux efficiency due to the slantly wound coils, have a low operational performance of conventional coreless motors. This adversely results in consuming more electricity to operate the motor properly and to generate a desired torque. Another problem of the conventional armature coils resides in that the production process of the coreless motors is complex, thus reducing productivity of the motors and increasing the production cost of the motors and thereby reducing economical efficiency of the motors.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a method of winding an armature coil, which winds the coil on a cylindrical resin insulator while maximizing magnetic flux efficiency of the coil and allows a resulting coreless motor to effectively generate desired torque by an application of a low current so as to conserve electricity, and to simplify the production process of the motor so as to reduce the production cost of the motor, thus finally improving productivity and economical efficiency of the coreless motors,
Another object of the present invention is to provide a coreless motor produced through such a coil winding method.
In order to accomplish the above object, the primary embodiment of the present invention provides a method of winding an armature coil on a cylindrical resin insulator of coreless motors, comprising the step of repeatedly winding the coil on the insulator in a way such that each turn of the coil primarily linearly extends on the upper surface of the insulator, vertically extends down on the sidewall of the insulator, and linearly extends on the lower surface of the insulator prior to vertically extending up on the sidewall of the insulator.
In an armature coil winding method according to the second embodiment of this invention, the coil is repeatedly wound on the cylindrical resin insulator in a way such that each turn of the coil primarily extends on the upper surface of the insulator while passing over the sidewall of an upper center projection of the insulator, vertically extends down on the sidewall of the insulator, and extends on the lower surface of the insulator while passing over the sidewall of a lower center projection prior to vertically extending up on the sidewall of the insulator.
The armature coil winding method of this invention improves magnetic flux efficiency of the coil, thus allowing a resulting coreless motor to precisely vibrate. The coreless motors, produced through the coil winding method of this invention, have improved operational reliability and improve the operational efficiency, operational reliability and market competitiveness of resulting cellular phones.